Antitarnish, antimicrobial copper alloys and surfaces made from such alloys

ABSTRACT

An antimicrobial, tarnish resistant copper alloy with a golden visual appearance comprising between about 1% and about 4% Ni, up to 3% Al, and optionally Zn and/or Mn up to a total of about 15%.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/259,837, filed on Nov. 10, 2009. The entire disclosure of the above application is incorporated herein by reference.

BACKGROUND

This invention relates to antimicrobial copper alloys, and to surfaces made from such alloys, and in particular to tarnish resistant antimicrobial copper alloys and surfaces made from such alloys.

Copper and copper alloys are known to have useful antimicrobial properties. These metals can kill human pathogens, including bacteria such as E. coli 0157, Listeria monocytogenes, Salmonella, and Methicillin-resistant Staphylococcus aureus (MRSA). The Environmental Protection Agency has declared that alloys containing 65% or more copper have inherent antimicrobial properties. See, Antimicrobial Copper Alloys Group I (EPA Reg. No. 82012-1), Antimicrobial Copper Alloys Group II (EPA Reg. No. 82012-2), Antimicrobial Copper Alloys Group III (EPA Reg. No. 82012-3), Antimicrobial Copper Alloys Group IV (EPA Reg. No. 82012-4), and Antimicrobial Copper Alloys Group V (EPA Reg. No. 82012-5), incorporated herein by reference.

Because of this antimicrobial property, copper and copper alloys would at first blush appear to be good candidates for fabricating surfaces in health care and food service facilities, and even in home and industrial settings. However copper's tendency to tarnish, which can be accelerated by the application of certain cleaners used in such environments, makes many copper alloys unsuitable for such uses. Tarnishing is psychologically and aesthetically undesirable for such surfaces, particularly in health care and food service institutions, where tarnished surfaces would appear unattractive and unclean. Furthermore, the distinctive copper color of many copper alloys limits their acceptability for some applications.

While some silver-toned tarnish-resistant antimicrobial copper alloys are known (e.g., C710), for at least some applications it is desirable to avoid silver-toned colors because these may be confused with more familiar silver-toned surfaces such as stainless steel, which while they can be sterilized, are not regarded as antimicrobial. C706 is another tarnish resistant antimicrobial copper alloy, but has a rose color, which may not be desirable for some applications.

SUMMARY

A preferred embodiment provides alloys with a combination of antimicrobial properties, attractive appearance, and tarnish resistance. Generally, the alloys of this preferred embodiment comprise at least 1% Ni, and up to 3% Al. (Percentages are weight percentages unless otherwise indicated.) In a more preferred embodiment, the alloys have a golden visual appearance, and contain Zn and/or Mn up to about 15%. Other elements that do not negatively impact tarnish resistance or antimicrobial activity of the alloy can be present.

DETAILED DESCRIPTION

Embodiments of this invention provide alloys, and surfaces made with such alloys, with a combination of antimicrobial properties, attractive appearance, and tarnish resistance. In a preferred embodiment, the alloy has an attractive golden visual appearance.

Generally the alloys of this preferred embodiment comprise between about 1 and about 4% Ni, and up to 3% Al. (Percentages are weight percentages unless otherwise indicated.) In a more preferred embodiment the alloys contain Zn and/or Mn up to about 15%. Other elements that do not negatively impact tarnish resistance or antimicrobial activity of the alloy can be present.

As detailed below, the inventors have observed that Cu—Zn alloys performed poorly both in touch and cleaning testing compared with other alloys; but that Cu—Ni alloys performed very well in both touch and cleaning testing. Resistance to tamishment by touching appears to be a more significant differentiator than other properties, such as resistance to cleaning agents and humidity.

Of the alloys that the EPA recognizes as antimicrobial, the inventors have found that alloys of Cu—Ni—Al provide a desirable combination of tarnish resistance and color, and that in particular alloys of Cu—Zn—Mn—Ni—Al, such as those identified herein as K475, K476, K589, K592, and K593 provide a desirable combination of antimicrobial activity, tarnish resistance, and a desirable golden visual appearance.

Nickel

In general, nickel is present in sufficient amounts to improve tarnish resistance. Generally, nickel in excess of about 1% improves tarnish resistance, and the nickel content is preferably at least 1.5%. In Cu—Ni—Al alloys the Ni content may be as high as 6.9% or higher. There is not necessarily an upper limit on nickel content, but nickel content is generally limited by its cost compared to the other alloying elements, and its effect, together with the other alloying elements, on the color of the alloy.

Aluminum

Aluminum improves resistance to tarnishnient from touching. Aluminum is preferably present in amounts up to about 3%. It is generally preferred that aluminum be present at a level of at least 0.6%. Additional aluminum above 3% does not appear to be necessary, and in amounts above about 8% to 11%, can negatively affect antimicrobial activity of the alloy. See, Use of Copper Cast Alloys to Control Escherichia coli 0157 Cross-Contamination During Food Processing, Applied and Environmental Microbiology, June 2006, pp. 4239-4244, incorporated herein by reference.

Zinc

Zinc, alone or in combination with manganese, improves the tarnish resistance of Ni—Cu and Ni—Al—Cu alloys, and affects their color. If zinc is present without manganese, then the zinc content is preferably at least about 6.8%, and preferably less than about 15%. If zinc and manganese are both present, zinc can be present in any amount, but it is preferable that the total content of zinc and manganese does not exceed a level which increases susceptibility to stress corrosion cracking, generally believed to be about 15%. Where both zinc and manganese are present, the zinc content is preferably between about 6.8% and about 10.8%. Considerations in setting the upper limit of the zinc content include resisting stress corrosion cracking, and maintaining desired color.

Manganese

Manganese, alone or in combination with zinc, improves the tarnish resistance of Ni—Cu and Ni—Al—Cu alloys, and affects their color. If manganese is present without zinc, then the manganese content is preferably at least about 4.8%, and preferably less than about 15%. If manganese and zinc are both present, manganese can be present in any amount, but it is preferable that the total content of zinc and manganese does not exceed a level which increases susceptibility to stress corrosion cracking, generally believed to be about 15%. Where both zinc and manganese are present, the manganese content is preferably between about 4.8% and about 6.9%. Considerations in setting the upper limit of the manganese content include resisting stress corrosion cracking, and maintaining desired color.

Total Zinc and Manganese Content

It is believed preferable to maintain the total content of Zn and Mn below a level which increases susceptibility to stress corrosion cracking, generally believed to be about 15%.

Experimental alloys (identified with prefix K) for Examples 1-5 were prepared by casting into 10 pound laboratory ingots. Alloys for Example 6 were prepared by direct chill casting into 7 inch×30 inch×25 foot bars. The production bars and laboratory ingots were both processed to mill plate by soaking at about 850° C. and hot rolling to between 0.5-0.6 inch thick. In each case, the hot rolled plate or coil was milled to remove surface oxides developed during hot rolling. The alloys were then processed to the condition in which they were tested by sequential cold rolling and annealing steps to produce the desired metallurgical condition.

Example 1

Eight commercial and four developmental alloys were subjected to cleaning, touch testing, and humidity testing.

The tested alloys (Table 1) were either as-rolled (AR) or roughened with Scotch-Brite® (SB).

TABLE 1 Alloys Used in Example 1 Alloy ID Composition C110 Cu C230 Cu—15Zn C260 Cu—25Zn C5248 Cu—10Sn + Fe, Ni C638 Cu—2.8Al—1.8Si + Co, Ni, Fe, Mn, Zn C706 Cu—10Ni—1.5Fe—1.0Mn—1.0Zn C710 Cu—10Ni—0.6Fe—0.5Mn—0.5Zn K444 Cu—18Mn—14Zn—1.5Al K445 Cu—17Mn—12Zn K451 Cu—10Mn—14Zn—3.75Ni K453 Cu—16Mn—12Zn—3Ni C713 Cu—25Ni—0.4Mn 304LSS Fe—19Cr—10Ni—0.03C (nominal composition) Compositions are analyzed compositions for K-alloys, and nominal compositions for all other alloys

Cleaning Testing

All the alloys were degreased with isopropyl alcohol before testing. The cleaners used, along with their respective measured pH, are given in Table 2.

TABLE 2 Cleaners used in Example 1 (with their measured pH) Measured ID Commercial Name, Ingredients if Provided pH PA Pro Bowl: phosphoric acid (8%) 0 WA Wex-All 1 HP Proxi ®: Hydrogen Peroxide (<8%) 2 F Fantastik (anti-microbial): measured pH 11 11 dimethyl benzyl ammonium chlorides .11% dimethyl ethylbenzyl ammonium chlorides .11% D Dawn ® Dish Soap:diluted with water (1:10) 8 WA-d Wex-All, diluted 1:128 water 4 P Purell © hand Cleaner, 62% ethyl alcohol 5

All samples were wiped with a cloth saturated with the cleaner (PA, WA, HP, and D) or sprayed (in the case of F), and wiped off twice daily with a minimum of 4 hours between cleanings for ten days. (Wex-All, which is a general disinfectant, was used at full strength and not according to the manufacturer's recommendation. At this strength Wex-All appeared to leave a film on the surface which could be readily removed with a 50:50 Wex-All solution. This film darkened over a period of several hours to overnight.) All tested alloys were judged by at least three independent judges according to the following criteria:

1 No Discoloration

2 Less than 60% light discoloration

3 More than 60% light discoloration—no dark areas

4 Complete discoloration-some very dark areas

5 Majority is dark discoloration.

with lower scores being better than higher scores. The results are reported in Table 3A.

In general, the more acidic cleaners had a much stronger effect on the alloys (particularly K444, K445, K451, and K453 and C110 and C230). These alloys contain either high Mn, and/or low Zn. It appears when comparing the C230 to the C260 that more Zn may be beneficial, while higher Mn may cause the alloy to be affected more strongly by acids. Alloy 0638, with Al+Si was also significantly affected by the acid-containing cleaners.

Because C110 and C230 performed poorly in the first round of testing, they were eliminated from further testing, and the remaining eight alloys, together with standard 304LSS were tested. The tested alloys (Table 1) were either as-rolled (AR) or roughened with Scotch-Brite® (SB). All were degreased with isopropyl alcohol before testing. Diluted Wex-All (WA-d) and Purell hand cleaner (P) (see Table 2) were used. Both cleaners were wiped on 2 times daily at least 4 hours apart. The cleaners were not wiped off. All tested alloys were judged by at least three independent judges according to using a 3 point, rather than the 5 point scale identified above:

1 Unchanged

2 Light discoloration—non uniform

3 Light discoloration—uniform

with lower scores being better than higher scores. The results are given in Table 3B.

New composite cleaning scores for the alloys were determined combining the scores for some of the cleaners used in part 1 and the two additional cleaners used in part 2. These are shown in Table 3C.

Touch Testing

Touch testing consisted of having a plurality of different people touch the samples of each of the alloys (except 304LSS) for 5 minutes twice daily for 21 days. Alloys were rotated among people each week for 3 weeks. All tested alloys were judged by at least three independent judges according to the following criteria:

1 Little if any discoloration

2 Light discoloring incomplete

3 Discolored more than 75% but not deep

4 Deep discolored spots

5 Complete and deep discoloration

with lower scores being better than higher scores. The results are reported in Table 4.

Humidity Testing

Resistance to humidity was tested by placing samples of each of the alloys (except 304LSS) in a humidity chamber at 28° C. and 95% humidity for 3 weeks. All tested alloys were judged by at least three independent judges according to the following criteria:

1 Slight water marking

2 Some water marks

3 Water marks no pits

4 Some pits with water marks

5 Many pits with water marks

with lower scores being better than higher scores. The results are reported in Table 5.

The results of the three tests were compiled, and are reported in Table 6A. Of the development alloys, K451 was the best performing, with a total score of 18. K451 had the lowest Mn of the development alloys, and contained 3.75% Ni. The results using the new cleaning scores of Table 3C and the touch scores of Table 4 and humidity scores of Table 5 are reported in Table 6B.

TABLE 3A Cleaning Test Results from Example 1, Part 1 Alloy C110 C230 C260 C5248 C638 C706 C710 K444 K445 K451 K453 C713 Condition Cleaners AR SB AR SB AR SB AR SB AR SB AR SB AR SB AR AR AR AR AR PA 5 5 4 5 3 4 2 2 5 5 2 3 2 2.5 5 5 4 4 2 WA 3 4 3 3 3 2 2 2 3 3 3 3 2 2 4 4 4 4 3 HP 3 3 3.5 3 1 1 1 2 2 3 1 2 1 1  1+  1° 1 1 1 F 5 3 4 3 1 2 1 1 3 3 1 1 1 1 2 2 1 2 1 D 5 4 5 4 1 2 3 3 3 4 1 1 1 1 2 2 2 1.5 1 Cleaning 21 19 19.5 18 9 11 9 10 16 18 8 10 7 7.5 14  14  12 12.5 8 Composite Score *specimens darkened over a period of a few hours to overnight. °Darkened overnight

TABLE 3B Cleaning Test Results from Example 1, Part 2 Alloy C260 C5248 C638 C706 C710 K444 K445 K451 K453 C713 304SS Condition Cleaners AR SB AR SB AR SB AR SB AR SB AR SB AR SB AR SB AR SB AR SB AR SB WA-d 3 2 3 3 3 3 2 1.5 1 1 1 1 2 1.5 3 2 2 2 2 1 1 1 P 2 2 2 2 2 2 2 2 1.5 2 2 2 2 2 2 2 2 2 2 2 2 2 Total 5 4 5 5 5 5 4 3.5 2.5 3 3 3 4 3.5 5 4 4 4 4 3 3 3 AR As-rolled SB Scotch-Brite ®

TABLE 3C Alloy 260 5248 638 706 710 K444 K445 K451 K453 713 Condition Cleaners AR SB AR SB AR SB AR SB AR SB AR AR AR AR AR Wex-All 3 2 3 3 3 3 2 1.5 1 1 1 2 3 2 2 Dillute Hand 2 2 2 2 2 2 2 2 1.5 2 2 2 2 2 2 cleaner Proxi 1 1 1 2 2 3 1 2 1 1  1+  1° 1 1 1 Fantastic 1 2 1 1 3 3 1 1 1 1 2 2 1 2 1 Dawn 1 2 3 3 3 4 1 1 1 1 2 2 2 1.5 1 Cleaning 8 9 10 11 13 15 7 7.5 5.5 6 7 8 9 8.5 7 total

TABLE 4 Touch Test Results for Example 1 Alloy 110 230 260 5248 638 706 710 K444 K445 K451 K453 C713 Condition AR SB AR SB AR SB AR SB AR SB AR SB AR SB AR AR AR AR AR Rating 3 4 4 3 3 3 3 2 4 5 2 1 1 1 3.5 3 3 3 1

TABLE 5 Humidity Test Results for Example 1 Alloy 110 230 260 5248 638 706 710 K444 K445 K451 K453 C713 Condition AR SB AR SB AR SB AR SB AR SB AR SB AR SB AR AR AR AR AR Rating 3 3 3 3 2 3 3 3 3 3 3 3 2 1 3 3.5 3 3 1

TABLE 6A Composite Score for Example 1 Alloy 110 230 260 5248 638 706 710 K444 K445 K451 K453 C713 Condition AR SB AR SB AR SB AR SB AR SB AR SB AR SB AR AR AR AR AR Touch + 6 7 7 6 5 6 6 5 7 8 5 4 3 2 6.5 6.5 6 6 2 Humidity Grand 27 26 26.5 24 14 17 15 15 23 26 13 14 10 9.5 20.5 20.5 18 18.5 10 Total

TABLE 6B using the cleaning scores from Table 3C and The Humidity and Touch scores from Tables 4 and 5 Alloy C260 C5248 C638 C706 C710 K444 K445 K451 K453 C713 Condition AR SB AR SB AR SB AR SB AR SB AR AR AR AR AR touch + 5 6 6 5 7 8 5 4 3 2 6.5 6.5 6 6 2 humidity Total 13 15 16 16 20 23 12 11.5 8.5 8 13.5 14.5 15 14.5 9

Example 2

Two commercial and seven developmental alloys and stainless steel were subjected to cleaning, touch testing, and humidity testing. The tested alloys (Table 1) were either as-rolled (AR) or roughened with Scotch-Brite® (SB).

TABLE 7 Alloys Used in Example 2 Alloy ID Composition C425 Cu—9.5Zn—2Sn C7025 Cu—3.0Ni—0.7Si—0.1Mg K513 Cu—3.0Sn—0.025P—0.02Fe K519 Cu—3.0Sn—10.0Zn—0.02Fe—0.01P K515 Cu—2.0Ni—1.5Sn—0.05Fe—0.05Mn—0.4Si K516 Cu—2.0Ni—1.5Sn—10Zn—0.05Fe—0.05Mn—0.4Si K475 Cu—7.8Zn—5.8Mn—2.1Ni—1.3Al K476 Cu—10.8Zn—5.8Mn—2.1Ni—0.6Al K477 Cu—8.8Zn—6.2Mn—2.1Ni 304L Fe—19Cr—9Ni—2Mn + C, N, etc. Compositions are analyzed compositions for K-alloys, nominal compositions for all other alloys

Cleaning Testing

All the alloys were degreased with isopropyl alcohol before testing. The cleaners used were Wex-All, diluted 1:128 with water (WA-d), Proxi® (HP), Fantastik® (anti-microbial) (F), and Dawn® Dish Soap diluted with water (1:10) (D).

All samples were wiped with a saturated cloth and wiped off (except the diluted Wex-All and Purell®, which were not wiped off) in the morning and at the end of the day for 2 weeks. Images were recorded every day in-between cleanings. All tested alloys were judged by at least three independent judges according to the following criteria:

1 No discoloration 2 Less than 60% light discoloration 3 More than 60% light discoloration—no dark areas 4 Complete discoloration-some very dark areas 5 Majority is dark discoloration. with lower scores being better than higher scores. The results are reported in Table 8. With the exception of C425, all copper alloys tested were adversely affected by Wex-All. Alloys C425, K516, K475, K476, and K477 all performed at or very close to stainless steel (304L) in these cleaning tests.

Touch Testing

Touch testing consisted of having a variety of people touch the samples of each of the alloys for 5 minutes twice daily for 21 days. Alloys were rotated among people each week for 3 weeks. All tested alloys were judged by at least three independent judges according to the following criteria:

1 Little if any discoloration 2 Light discoloring incomplete 3 Discolored more than 75% but not deep 4 Deep discolored spots 5 Complete and deep discoloration with lower scores being better than higher scores. The results are reported in Table 9.

Humidity Testing

Resistance to humidity was tested by placing samples of each of the alloys in a humidity chamber at 28° C. and 95% humidity for 3 weeks. All tested alloys were judged by at least three independent judges according to the following criteria:

1 Slight water marking 2 Some water marks 3 Water marks no pits 4 Some pits with water marks 5 Many pits with water marks with lower scores being better than higher scores. The results are reported in Table 9.

K475 performed equal to stainless steel in both the touching and humidity tests. The other two developmental alloys, K476 and K477 both are very close in performance to the stainless. These alloys appear to be relatively unaffected by humidity or human touch in this testing. The combination of Ni+Al appears to be beneficial to resistance from tarnishing from touching and humidity, at least under these testing conditions.

TABLE 8 Cleaning Test Results for Example 2 Alloy C425 C7025 K513 K519 K515 K516 K475 K476 K477 304L Condition Cleaners AR SB AR SB AR SB AR SB AR SB AR SB AR SB AR SB AR SB AR SB Wex All 3 2 3 2 3 3 3 3 3 3 3 3 2 3 3 3 3 3 1.5 1 Dilute Proxi ® 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Fantastik ® 1.5 1 1.5 1 1.5 1 1 1 1 1.5 1 1 1 1 1 1 1 1 1 1 Dawn ® 2 1 2 1.5 1.5 2 1.5 1.5 2 2 1.5 1 1 1.5 1 1 1 1.5 1 1 total 7.5 5 7.5 5.5 7 7 6.5 6.5 7 7.5 6.5 6 5 6.5 6 6 6 6.5 4.5 4 composite w/o WAD 4.5 3 4.5 3.5 4 4 3.5 3.5 4 4.5 3.5 3 3 3.5 3 3 3 3.5 3 3

TABLE 9 Humidity and Touch Testing Results for Example 2 Alloy C425 C7025 K513 K519 K515 K516 K475 K476 K477 304L Condition AR SB AR SB AR SB AR SB AR SB AR SB AR SB AR SB AR SB AR SB Humidity 1 2 3 2.5 3 3 3 2 3 3 3 3 1 1 2 2 1 2 1 1 Touch 5 5 5 5 1.5 1.5 3 3 4 3 3 3 1 1 1 1 2 2 1 1 Total 6 7 8 7.5 4.5 4.5 6 5 7 6 6 6 2 2 3 3 3 4 2 2

Example 3

Several alloys were prepared (see Table 10), and their mechanical properties compared (see Table 11).

TABLE 10 Method of Preparing Alloys in Example 3 K538 Cast, Roll 90% Anneal 520° C./1.5 h Roll 20.5% Stress Relief at 300° C./3 h K539 Cast, Roll 90% Anneal 520° C./1.5 h Roll 20.5% Stress Relief at 300° C./3 h K540 Cast, Roll 90% Anneal 550° C./2 h Roll 20.5% Stress Relief at 300° C./3 h K541 Cast, Roll 90% Anneal 650° C./3 h Roll 20.5% Stress Relief at 300° C./3 h K542 Cast, Roll 90% Anneal 520° C./1.5 h Roll 20.5% Stress Relief at 300° C./3 h K543 Cast, Roll 90% Anneal 520° C./1.5 h Roll 20.5% Stress Relief at 300° C./3 h K475A Cast, Roll 90% Anneal 650° C./3 h Roll 20.5% Stress Relief at 300° C./3 h K476 Cast, Roll 90% Anneal 550° C./2 h Roll 20.5% Stress Relief at 300° C./3 h

TABLE 11 Mechanical Properties for Selected Antimicrobial Alloys Bends Zn Mn V Al Ni/Al YS (KSI) TS (KSI) EL (%) GW BW K538 9.9 6 0 0 na 60.1 66.8 15.8 0.63 0.57 K539 9.5 7.5 0.95 1.2 0.8 71.1 78.3 14.9 0.96 0.57 K540 10.3 6.5 2.1 1.25 1.7 82.6 87.8 15.2 0.68 1.78 K541 9.8 6.3 3.1 1.2 2.6 58.4 69.6 13.6 1.34 0.89 K542 0 0 2.2 2.2 1 65.4 68.8 16.1 0.63 1.34 K543 0 0 3.2 1.15 2.8 58.4 61.4 13.3 0.86 0.89 K475A 7.5 6.2 3.1 1.7 1.8 59.4 68.9 15.6 1.78 0.91 K476 10.8 5.8 2.1 0.6 3.5 69.7 76.3 15.0 0.89 1.03

Table 12 collects the results of the testing from Examples 1 through 3. In particular, data for alloys K538-K543 and alloys K589-K602 comes from testing, in accordance with the procedures set forth in Example 2. In Table 12, alloys with clean test scores of less than 4.5 and touch test scores of 2 or less are indicated as having “good” tarnish resistance.

Color information for selected alloys is also indicated in Table 12, based upon the following comparative scale:

W++ (C713) 0 Super White W+ 0.5 Very White W 1 White W− or WG 1.5 White-Gold YG 2 Yellow-Gold G 2.5 Gold Cu 3 Copper Cu− 3.5 Light Copper RG 4 Red-Gold As disclosed in co-assigned U.S. Pat. No. 6,432,556 (incorporated herein by reference), color determination may be by spectroscopy or other objective means. Instruments, such as provided by Hunter Associates Laboratory, Inc. of Reston, Va., quantify color according to a lightness attribute commonly referred to as “value” and two chromatic attributes commonly referred to as “hue” and “chroma”. Hue is color perception, the recognition of an object as green, blue, red, yellow, etc. Chroma is color concentration and ranges from grey to pure hue. Value is the lightness of the color and ranges from white to black. One method of specifying color is by a CIELAB scale. CIE stands for Commission Internationale de l'Eclairage (International Commission on Illumination) and. LAB stands for the Hunter L,a,b scale. The CIELAB color chart expresses hue as a combination of an a* value and a b* value extending arcuately about the color chart, with +a* being red, −a* being green, +b* being yellow and −b* being blue. Chroma is expressed as a value from the center of the circle with the center (0) being grey and +/−60 being full richness of the specified color. Value is expressed as an L* number ranging from white to black, such that the combination of hue, chroma and lightness represents a specific point on a three-dimensional sphere and a specific color.

Thus, alloys K513, K475, K475A, K476, K477, K589, K592, K593, and K599 provide antimicrobial materials with good tarnish resistance. Further, alloys K475, K475A and K476 provides antimicrobial materials with good tarnish resistance and a whitish golden color, and alloy K477 provides an antimicrobial material with good tarnish resistance and a yellowish golden color.

Tables 13-15 show mechanical properties for some of the alloys in Table 12.

Table 16 is a table of other possible antimicrobial, tarnish-resistant alloys, with desirable appearance and color traits.

TABLE 12 Cleaning Ni/Al Score: Touch Tarnish Alloy Condition Zn Mn Ni Al ratio Sn other P, F, D Score Resistance Color C110 AR 0 0 0 0 0 0 0 13 3 C110 SB 0 0 0 0 0 0 0 10 4 C230 AR 15 0 0 0 0 0 0 12.5 4 C230 SB 15 0 0 0 0 0 0 10 3 C260 AR 30 0 0 0 0 0 0 3 3 C260 SB 30 0 0 0 0 0 0 5 3 C5248 AR 0 0 0 0 0 10 Fe, Ni 5 3 C5248 SB 0 0 0 0 0 10 Fe, Ni 6 2 C638 AR 0 0 0 2.8 0 0 1.8Si, Mn, Co, Ni, Fe, 8 4 Zn C638 SB 0 0 0 2.8 0 0 1.8Si, Mn, Co, Ni, Fe, 10 5 Zn C706 AR 1 1 10 0 0 0 1.5Fe 3 2 Good C706 SB 1 1 10 0 0 0 1.5Fe 4 1 Good C710 AR 0.5 0.5 10 0 0 0 0.6Fe 3 1 Good C710 SB 0.5 0.5 10 0 0 0 0.6Fe 3 1 Good K444 AR 14 18 0 1.5 0 0 0 5 3.5 W++ K445 AR 12 17 0 0 0 0 0 5 3 W++ K451 AR 14 10 3.75 0 0 0 0 4 3 W− K453 AR 12 16 3 0 0 0 0 4.5 3 W++ C713 AR 0 0.4 25 0 0 0 0 3 1 Good W++ C425 AR 9.5 0 0 0 0 2 Fe and P 4.5 5 C425 SB 9.5 0 0 0 0 2 Fe and P 3 5 C7025 AR 0 0.1 3 0 0 0 Mg, 0.7Si, Fe 4.5 5 C7025 SB 0 0.1 3 0 0 0 Mg, 0.7Si, Fe 3.5 5 K513 AR 0 0 0 0 0 3 P and Fe 4 1.5 Good K513 SB 0 0 0 0 0 3 P and Fe 4 1.5 Good K519 AR 10 0 0 0 0 3 P and Fe 3.5 3 K519 SB 10 0 0 0 0 3 P and Fe 3.5 3 K515 AR 0 0 2 0 0 1.5 Mg, 0.4Si, Fe 4 4 K515 SB 0 0 2 0 0 1.5 Mg, 0.4Si, Fe 4.5 3 K516 AR 10 0 2 0 0 1.5 Mg, 0.4Si, Fe 3.5 3 K516 SB 10 0 2 0 0 1.5 Mg, 0.4Si, Fe 3 3 K475 AR 7.8 5.8 2.1 1.3 1.62 0 0 3 1 Good WG K475 SB 7.8 5.8 2.1 1.3 1.62 0 0 3.5 1 Good WG K476 AR 10.8 5.8 2.1 0.6 3.50 0 0 3 1 Good WG K476 SB 10.8 5.8 2.1 0.6 3.50 0 0 3 1 Good WG K477 AR 8.8 6.2 2.1 0 0 0 0 3 2 Good YG K477 SB 8.8 6.2 2.1 0 0 0 0 3.5 2 Good YG SS304L SB 0 2 9 0 0 0 Fe—19Cr + N + C 3 1 Good SS304L AR 0 2 9 0 0 0 Fe—19Cr + N + C 3 1 Good K538 AR 9.9 6 0 0 0 0 0 6 2 K539 AR 9.5 7.5 0.95 1.2 0.79 0.00 0 4.5 2 K540 AR 10.3 6.5 2.1 1.25 1.68 0.00 0 5 1.5 K541 AR 9.8 6.3 3.1 1.2 2.58 0.00 0 4.5 1.5 K542 AR 0 0 2.2 2.2 1.00 0.00 0 5.5 3 K543 AR 0 0 3.2 1.15 2.78 0.00 0 5.5 1 K589 AR 8.2 6.1 3.05 0.9 3.39 0.00 0 4 1.2 Good K590 AR 10.2 5 3.1 1.4 2.21 0.00 0 4.5 1.2 K591 AR 10 5.1 2.5 0.95 2.63 0.00 0 5 1.2 K592 AR 10.3 5 1.5 1.15 1.30 0.00 0 4 1.5 Good K593 AR 6.8 5.1 3.1 1.4 2.21 0.00 0 3.5 1.5 Good K594 AR 25.4 0 3 1.2 2.50 0.00 0 Broke on rolling K595 AR 0 0 2.95 0.9 3.28 0.00 0 4.5 3 K596 AR 0 0 1.45 0.7 2.07 0.00 0 6 3 K597 AR 0 0 2 1.3 1.54 0.00 0 5.5 3 K598 AR 0 0 2.95 1.9 1.55 0.00 0 4.5 2 K599 AR 0 0 3.07 1.62 1.90 0.00 0 4 1.5 Good K600 AR 0 0 2 1.6 1.25 0.00 0 4 2 K475A AR 7.5 6.2 3.1 1.7 1.24 0.00 0 3 1 Good WG K602 AR 0 0 2 7.7 0.26 0.00 0 5 1 Compositions are analyzed compositions for K-alloys, nominal compositions for all other alloys

TABLE 13 Mechanical Properties Cold Rolled to 90% + Annealed at 520° C. 75 m Properties @.050 Gauge % Gauge TS YS Elong IACS Zn Mn Ni Al K475A 0.0506 85.5 74.6 19.9 6.3 7.5 6.2 3.1 1.7 K476 0.0498 68.8 51.7 28.9 6.4 10.8 5.8 2.1 0.6 K538 0.0488 53.7 26 36.1 6.8 9.9 6 0 0 K539 0.0506 63.1 34.3 35.2 5.3 9.5 7.5 0.95 1.2 K540 0.0502 74.1 54.8 27.6 6 10.3 6.5 2.1 1.25 K541 0.0501 79.8 65.4 23.1 6.2 9.8 6.3 3.1 1.2 K542 0.0477 54.3 33.8 32.7 21.6 0 0 2.2 2.2 K543 0.0484 48.2 28.4 31.6 24.2 0 0 3.2 1.15

TABLE 14 Mechanical Properties Cold Rolled to 90% + Annealed at 520° C. 75 m + Coled Rolled 30% + Stress Relief at 250° C. 120 minutes Properties @.035 Gauge 90 deg Bends Gauge TS YS Elong GW BW K475A 0.0344 116.1 112.2 2 1.8 7.3 K476 0.0347 97.8 95.7 5.9 0.8 1.8 K538 0.0346 75.8 73.6 7.8 0.7 1.4 K539 0.0346 92.1 89.9 6.6 0.8 1.4 K540 0.0347 106.1 103.2 3.3 1.4 1.8 K541 0.0291 117.3 113.8 0.7 2.7 8.6 K542 0.0295 79.7 78 4.2 0.7 1.2 K543 0.0346 66 65 5.2 0.8 1.8

TABLE 15 Mechanical Properties Cold Rolled to 90% + Annealed at 520° C. 75 m + Cold Rolled 30% + Stress Relief at 470° C. 60 minutes Properties @.035 Gauge 90 deg Bends Gauge TS YS Elong GW BW K541 0.0290 80.2 61.5 23.8 0.0 0.0

Example 4

Alloys in Table 16, plus additional alloys were subjected to touch and cleaning tests (reported in Table 17). The sample preparation differed somewhat for these tests. The results in Table 17 were performed on samples which were polished smooth and degreased prior to testing, to remove surface imperfections in order to minimize test variables. Touch testing was done as before using a variety of people touching the samples of each of the alloys for 5 minutes twice daily for 21 days. Alloys were rotated among people each week for 3 weeks. All tested alloys were judged by at least three independent judges according to the following criteria:

1 Little if any discoloration

2 Light discoloring incomplete

3 Discolored more than 75% but not deep

4 Deep discolored spots

5 Complete and deep discoloration

with lower scores being better than higher scores. The results are reported in Table 17.

Samples of the same alloys were subjected to cleaning testing; again these samples were polished smooth and degreased. The cleaners used were, CleanCide Wipes (CleanCide), Proxi®, Fantastik® (anti-microbial), and Dawn® Dish Soap diluted with water (1:10)). All samples were wiped with a saturated cloth and wiped off, except the in case of CleanCide wipes which were wiped on without being wiped off, twice daily in the morning and at the end of the day for 2 weeks. All tested alloys were judged by at least three independent judges according to the following criteria:

1 No discoloration

2 Less than 60% light discoloration

3 More than 60% light discoloration—no dark areas

4 Complete discoloration-some very dark areas

5 Majority is dark discoloration.

with lower scores being better than higher scores. Commercial alloy C752 was included as a standard. The alloy did very well through the testing.

None of the experimental alloys K603-K637 performed well with CleanCide, but they generally performed well in the other cleaners and the touch tests. There are some slight differences within this group, such as alloys with lower Mn did slightly better than those with higher levels, e.g., K610 versus K604.

TABLE 16* Additional Antimicrobial, Tarnish Resistant Alloys Composition, weight % Ingot Zn Mn Ni Al K603 7.4 4.9 2.1 1.3 K604 7.5 5.0 2.0 2.0 K605 7.7 5.2 3.0 1.1 K606 7.7 5.1 3.1 2.0 K607 7.4 6.0 2.1 1.15 K608 7.4 6.2 2.1 2.0 K609 7.5 5.9 3.0 1.15 K610 7.5 6.9 3.0 2.0 K611 8.5 5.3 1.9 1.2 K612 8.5 5.0 1.9 2.1 K613 8.6 5.1 3.1 0.90 K614 8.5 5.0 3.1 2.0 K615 8.4 6.0 2.1 1.2 K616 8.3 6.2 2.1 1.9 K617 8.7 5.9 3.1 1.2 K618 8.9 6.3 3.0 2.0 K619 — — 6.4 3.0 K620 — — 3.4 1.9 K621 — — 2.1 3.0 K622 7.5 5.9 3.0 2.0 *Alloys with the same numbers have the same compositions, but there are slight variations in the reported compositions due to improvements in measuring techniques.

TABLE 17 Touch and Cleaning Test Results from Example 4 Zn Mn Ni Al Touch #2 CleanCide Proxi ® Fantastik ® Dawn ® K603 7.4 4.9 2.1 1.3 1 2 1 1 1 K604 7.5 5 2 2 1 2 1 1 1 K605 7.7 5.2 3 1.1 1 2 1 1 1 K606 7.7 5.1 3.1 2 1 2 1.5 1 1 K607 7.4 6 2.1 1.15 1 2.5 1 1 1 K608 7.4 6.2 2.1 2 1 3 1.5 1.5 1 K609 7.5 5.9 3 1.15 1.5 2.5 2 1.5 1 K610 7.5 6.9 3 2 1 3 1.5 1.5 1.5 K611 8.5 5.3 1.9 1.2 1 3 1 1t 1 K612 8.5 5 1.9 2.1 1 2.5 1 1 1 K613 8.6 5.1 3.1 0.9 2 2.5 1 1 1 K614 8.5 5 3.1 2 2 2 1.5 1 1 K615 8.4 6 2.1 1.2 2* 2 1.5 1 1 K616 8.3 6.2 2.1 1.9 1* 2 1 1 1 K617 8.7 5.9 3.1 1.2 1* 2 1 1 1 K618 8.9 6.3 3 2 1* 2 2 1 1 K619 0 0 6.4 3 2 2 2 1 1 K620 0 0 3.4 1.9 1 2 2 1 1 K621 0 0 2.1 3 2 2.5 2 1 1 K622 7.5 5.9 3 2 1 2 1.5 1 1 K636 7.58 6.08 2.43 1.32 1 2 1.5 1 1 K637 8.08 5.46 2.75 1.73 1 2 1.5 1 1 C752 Cu—18N I-17-Zn 1 2 1 1 1 K513 Cu—3.0 Sn—0.025P0.02Fe 1.5 2 1 1 3 K633 Cu—2.9 Sn 4 3 1 1 2 K635 Cu—3.3 Sn—0.018P—0.01 Fe 4 2 1 1 3 nm: not measured *these samples were only degreased and not polished smooth

Example 5

An alloy with composition of about Cu-7.75 Zn-5.75 Mn-2.5 Ni-1.5 Al would give good cleaning and touch results based upon the results of Example 4. A new series of alloys were cast, hot rolled HR75% (reduction in thickness), milled and cold rolled CR 92%, annealed under different conditions and given a small 10-14% final reduction. The compositions and mechanical test results are reported in Table 18. Alloys in Table 18 were cleaned and evaluated as in Example 4. All alloys scored 1 when cleaned with Proxi®, Dawn® diluted with water (1:10), and antimicrobial Fantastik. As before, the alloys did poorly when cleaned with CleanCide wipes, rating 3-4.

TABLE 18 Mechanical testing results from Example 5 CR (92%) 0.035ga CR (92%) 0.035ga 750 C./15 s 780 C./10 s Alloy Chemistry as-annealed +14% CR as-annealed +14% CR No Zn Mn Ni Al TS YS EL TS YS EL TS YS EL TS YS EL K676 7.77 5.60 2.26 1.23 64 35 37 74 69 10 61 30 36 73 67 11 K677 7.72 5.72 2.75 1.21 66 38 31 73 65 15 63 31 38 77 70 11 K678 7.85 5.75 2.26 1.7 64 32 33 75 68 16 63 30 32 76 69 15 K679 7.7 5.67 2.72 1.7 75 53 27 77 69 14 65 32 32 77 63 14 K680 7.82 6.24 2.26 1.22 65 33 34 73 66 14 62 29 36 74 67 18 K681 7.71 6.29 2.73 1.24 65 33 34 76 70 15 64 31 36 77 71 14 K682 7.75 6.25 2.24 1.74 64 29 39 76 68 17 64 30 38 78 70 16 K683 7.71 6.25 2.74 1.75 74 49 29 78 70 14 66 32 36 78 68 14 K684 8.32 5.71 2.25 1.2 65 36 34 72 64 15 62 31 35 76 68 12 K685 8.1 5.49 2.76 1.24 65 35 35 72 64 16 64 35 35 78 68 12 K687 8.1 5.49 2.76 1.75 78 60 25 79 73 12 66 34 35 79 72 14 K688 7.64 6.02 2.26 1.25 64 33 34 72 67 15 63 32 35 76 70 12 K689 8.02 5.88 2.75 1.22 65 35 34 73 66 14 64 32 35 78 74 9 K690 8.23 6.02 2.28 1.74 65 33 35 77 70 16 65 31 35 78 70 12 K691 8.04 5.94 2.75 1.72 66 33 34 79 72 13 65 32 38 81 74 14 K692 7.86 5.24 2.5 1.45 65 35 34 73 65 16 63 31 37 75 69 12 K693 7.68 5.14 2.27 1.23 66 42 34 70 63 15 61 29 39 73 68 13 K694 7.58 5.96 2.75 1.22 65 36 34 73 67 15 64 34 37 77 72 13 K695 8.09 5.49 2.28 1.22 63 33 36 72 66 14 60 27 36 72 66 13 K696 7.63 5.45 2.25 1.75 65 33 36 74 64 14 63 31 37 77 70 17

Example 6

An alloy was cast at a production level of the composition, Cu-7.75 Zn-5.38 Mn-2.51 Ni-1.61 Al. The overall process used was:

HRP 93% 850° C.→CR 90-94%→SA 750° C.→CR 10-12%

Four items were made, one as-annealed the other 3 were one quarter hard (H01); i.e. cold rolled CR10-12% s. The plant trial results are given in Table 19.

TABLE 19 Average mechanical properties of plant trial material Bends MBR/t MBR/t ga (in) YS KSI) TS (KSI) % EL GW BW Item 1 (H01) 0.0307 65.5 74.4 19.5 0.1 0.0 Item 2 (H01) 0.0390 65.3 74.1 19.3 0.1 0.0 Item 3 (H01) 0.0472 67.3 75.8 19.1 0.2 0.0 Item 4 (soft) 0.0472 31.6 64.7 36.0 0.0 0.0

Stress Corrosion Cracking (SCC) Testing

Due to the envisioned service conditions for this alloy, stress corrosion susceptibility testing was initiated in Mattsson's solution, in accordance with ASTM G37-98. Mattsson's solution is composed of copper sulfate pentahydrate, ammonium sulfate, and ammonium hydroxide in water. The pH is controlled from 7.1 to 7.5, the region of highest SCC susceptibility. Test specimens are examined periodically for cracks under a stereo microscope at 30×. A visible penetrating crack is judged a failure. In addition, the samples are evaluated for stress relaxation. If the remaining stress on the sample falls below 80% of the original stress level, the sample has failed. The recommended test duration in ASTM G37-98 is 1000 hours. It is customary to consider that survival of at least 1000 hours in this test indicates that the material is essentially immune to SCC. Samples of Item 1 (Table 19) as-received and with a relief anneal of 300° C./1 h have been tested in Mattsson's solution. All three samples of Item 1 in the as-received condition completed the test without failure as did 2 of the 3 samples of Item 1 which were relief annealed. One sample of Item 1 with the relief anneal, failed at 648 hours. The cause of the failure is not known. The plant trial material is not susceptible to SCC in Mattsson's solution.

Color Analysis

All of the alloys plus the plant trial material was evaluated for color using, a standard condition; 10 degree observer using average daylight D65. The color measurement method is accordance with paragraph 35 in this document and is as described in U.S. Pat. No. 6,432,556, incorporated by reference herein Table 20 presents the results on the alloys from Tables 18 and 19. The terms in the table are L* is light to dark, C* is aroma, h* is hue, a* and b* are the locations on the plane in space defined by L*, C* and h*. These terms are further explained in http://www.hunterlab.com/manuals/appendixa2_(—)5.pdf incorporated herein by reference. The dEcmc(1:c=2.0) is calculated from the color measurements and is used to compare color measurements. All alloys in Table 20 are compared to plant trial material. Note that there are no dEcmc(1:c=2.0)values over 1.1 therefore, all these alloys appear to have the same color to the human eye.

TABLE 20 Color measurements using CIELAB scale. dEcmc (1:c = 2.0) is used to compare color measurements. See text for explanation. CIE D65/10 D65/10 Sample ID L* a* b* C* h* dEcmc (I:c = 2.0) Plant trial 86.90 1.74 14.04 14.15 82.95 0 Material K696 87.29 1.55 14.02 14.11 83.71 0.28 K694 86.66 1.94 12.68 12.82 81.31 1.07 K689 86.86 1.78 12.60 12.73 81.98 1.06 K685 87.05 1.81 13.79 13.91 82.50 0.23 K683 86.40 1.41 13.57 13.65 84.08 0.53 K687 87.37 1.32 13.41 13.47 84.37 0.67 K684 87.29 1.76 13.26 13.37 82.45 0.59 K676 86.22 2.25 14.07 14.25 80.91 0.69 K679 87.03 1.46 13.24 13.32 83.70 0.64 K690 87.00 1.33 13.69 13.75 84.46 0.55 K680 86.56 1.90 13.21 13.34 81.83 0.68 K681 86.75 1.79 12.66 12.78 81.95 1.02 K693 87.06 2.15 13.57 13.74 81.01 0.67 K678 86.94 1.47 14.45 14.52 84.18 0.48 K695 86.51 2.02 13.84 13.99 81.69 0.44 K692 87.39 1.68 13.87 13.97 83.10 0.22 K682 86.84 1.39 13.56 13.63 84.16 0.53 K677 86.94 1.92 13.40 13.53 81.86 0.55 K688 86.75 1.99 13.26 13.40 81.47 0.70 K691 86.91 1.30 13.05 13.11 84.30 0.85

Antimicrobial Testing

Samples of Item 2 in Table 19 were tested for resistance to microbial growth. The test methodology used was based on ASTM 1153-03, “Standard Method for Efficacy of Sanitizers Recommended for the Inanimate non-Food Contact Surfaces”. The materials were cleaned and degreased and inoculated with methicillin resistant staphylococcus aureus, (MRSA). Growth was monitored on the copper alloy and a stainless steel control for 1, 2 and 4 hours at 21° C. Triplicate samples were used in the study. The stainless steel control colonized additional bacteria as time progressed, no bacteria were found on any of the copper specimens at 1, 2 or 4 hours. The inoculation and counting methods used were in accord with ASTM 1153-03. The copper alloy of Item 2 was demonstrated antimicrobial under the test conditions. Table 21 shows the percent reduction of MRSA over time on Item 2 (Table 19).

TABLE 21 Reduction in MRSA on Item 2 (Table 19) over time Test Organism Exposure Time Carrier # Percent Reduction Methicillin 1 hour 1 >99.9999% Resistant 2 Staphylococcus 3 aureus- MRSA 2 hours 1 >99.9999% (ATCC 33592) 2 3 4 hours 1 >99.9999% 2 3

Nickel Release

Nickel can cause some people to have an adverse reaction. It is a desirable, but not necessary property that the alloy has low Ni release. Various methods of determining whether an alloy would release enough nickel to cause reactions in individuals with sensitivity to nickel are known. One such test consists of mixing solutions of dimethylglyoxime and ammonium hydroxide on the surface of the test article. If nickel is released, a light pink to red color results on the test article. Additional information about such testing is disclosed in http://corrosion-doctors.org/Allergies/nickelallergy.htm, incorporated herein by reference; and in Screening Tests For Nickel Release From Alloys And Coatings In. Items That Come Into Direct And Prolonged Contact With The Skin, PD CR 12471:2002 by British Standards Institution on ERC Specs and Standards. 

1. An antimicrobial, tarnish resistant copper alloy comprising at least about 1% Ni and up to 3% Al.
 2. The antimicrobial, tarnish resistant copper alloy according to claim 1 wherein the Ni content is at least about 1.5%.
 3. The antimicrobial, tarnish resistant copper alloy according to claim 1 wherein the Ni content is between about 1.5% and about 6.5%.
 4. The antimicrobial, tarnish resistant copper alloy according to claim 1 wherein the Ni content is at least about 2.9% and the Al content is at least about 1.8%.
 5. The antimicrobial, tarnish resistant copper alloy according to claim 1 wherein the alloy has a golden visual appearance, and further comprises at least one of Zn and Mn in amounts such that Zn+Mn<15%.
 6. The antimicrobial, tarnish resistant copper alloy according to claim 5 wherein the Mn content is
 0. 7. The antimicrobial, tarnish resistant copper alloy according to claim 5 wherein the Zn content is
 0. 8. The antimicrobial, tarnish resistant copper alloy according to claim 5 wherein the Zn content is between about 6% and about 12%, and the Mn content is between about 4% and about 7%.
 9. The antimicrobial, tarnish resistant copper alloy according to claim 8 wherein the Zn content is between about 6.8% and about 10.8%, and the Mn content is between about 4.8% and about 6.9%.
 10. The antimicrobial, tarnish resistant copper alloy according to claim 1 wherein the Ni content is between about 1.5% and about 3.1%, and the Al content is between about 0.5% and about 1.5%.
 11. The antimicrobial, tarnish resistant copper alloy according to claim 10 wherein the Zn content is between about 7.5% and about 10.5%, and the Mn content is between about 5% and about 6.5%.
 12. An antimicrobial, tarnish resistant copper alloy with a golden visual appearance comprising between about 1.5% and about 6.5% Ni, between about 0.6% and about 3.2% Al, and at least one of Zn and Mn in amounts such that Zn+Mn<15%.
 13. The antimicrobial, tarnish resistant copper alloy with a golden visual appearance of claim 12 comprising both Zn and Mn.
 14. The antimicrobial, tarnish resistant copper alloy with a golden visual appearance of claim 13, further comprising between about 6.8% and about 10.8% Zn and between about 4.8% and about 6.9% Mn.
 15. An antimicrobial, tarnish resistant copper alloy with a golden visual appearance comprising between about 7.8% and about 10.8% Zn, between about 5% and about 6.5% Mn, between about 2.1% and about 3.1% Ni, and up to about 1.4% Al.
 16. An antimicrobial, tarnish resistant copper alloy with a golden visual appearance comprising between about 2% and about 3% Ni, between about 1% and about 2% Al, between about 7.5% and about 8.5% Zn, and between about 5% and about 6% Mn. 